SEA FISHERIES INSTITUTE IN GDYNIA
Gdynia, Poland
Results of the Polish fishing survey of Greenland halibut (Reinhardtius hippoglossoides) in the Svalbard Protection Zone
(ICES IIb) in April 2007
Jerzy Janusz, Kordian Trella Sea Fisheries Institute, Kollataja 1, 81-332 Gdynia, Poland
jjanusz@mir.gdynia.pl
Gdynia, July 2007
1.INTRODUCTION... 3
2.MATERIALS AND METHODS... 3
3.VESSEL AND GEAR SPECIFICATIONS... 5
3. 1. Characteristics of the vessel ... 5
3. 2. Description of gear... 6
4.RESULTS... 6
4. 1. Species composition of catches... 6
4. 2. Catch rates ... 7
4. 3. Biological characteristics of Greenland halibut... 7
4. 4. Density, abundance, and biomass of Greenland halibut in the survey area... 9
4. 5. Other information... 9
TABLES... 10
FIGURES ... 17
ANNEX3... 27
1. Introduction
The Polish bottom fishing survey on Greenland halibut (Reinhardtius hippoglossoides) was conducted in April 2007 in the Svalbard Protection Zone (ICES IIb) and was the continuation of the Polish survey carried out in October 2006. The investigations were conducted based on the Polish application to and permission granted by the Directorate of Fisheries in Bergen, Norway. The Polish operating authority was the Sea Fisheries Institute in Gdynia (MIR) in cooperation with the North Atlantic Producers Organization Ltd. (PAOP sp. z o.o.).
The main objectives of the survey were:
• to determine the biological structure of Greenland halibut (Reinhardtius hippoglossoides);
• to determine the distribution, density, and standing biomass of Greenland halibut in the survey area;
• to determine the species composition of catches;
• to determine the incidental mortality of birds and mammals.
2. Materials and Methods
The surveys took place from 1 to 12 April 2007 and were conducted at a depth range of 500 to 1200 meters on the west slope of Bear Island and Svalbard covering the area between latitude 73o 30’N and 76o 30’N. The fishing vessel POLONUS (Fig.
1), which deployed a bottom trawl, was engaged in the survey. The research team comprised of two MIR scientists collected fisheries and biological data aboard the vessel. Samples were taken at three depth strata – shallower 500-699 m (S) deeper 700-999 m (D), and deepest 1000-1200 m (DD). The depth strata were divided into parallel sections of 10 nautical miles which created squares limited by depth strata.
The surface was divided into a total of 54 designated squares (Fig. 2). The surface of each square was calculated using the ArcGIS program. Calculations were made for each square between isobaths obtained from data on the International Bathymetric Chart of the Arctic Ocean (IBCAO) and the SRTM30_Plus model (Shuttle Radar Topography Mission).
Fifty three hauls were performed during 12 effective fishing days. At least one haul was carried out in each square of shallower and deeper strata. Since it was determined that the abundance of Greenland halibut in the deepest strata was very
was no haul. The density of fish in this square was calculated as the same as that in square DD-2. The positions of starting the hauls and directions of trawling are presented in Figure 3.The mean speed of vessel during trawling was about 3.1 knots.
The fishing data recorded for each haul included the following: date, time and position of start and end of the tow, duration and depth of tow, vessel speed, and catch data. The temperature of the water at depth of trawling was also recorded.
Each haul was sorted by species to determine the species composition of catches.
The bycatch species were separated from the Greenland halibut and then weighed, counted, and recorded; this provided information on the species composition of the catches by number and weight.
Samples of Greenland halibut, the target species, were collected for length measurements and biological analysis. The fish for length measurement (total length) were collected randomly from the conveyer and measured rounding down to the nearest centimeter. In total, 6085 specimens of Greenland halibut segregated by sex were measured, and 262 fish were taken for biological analysis. Each analysis included recording data concerning length, weight (to the nearest 10 g) sex, gonad maturity, and fullness of stomach. Otoliths were collected for later age determination.
Whole otoliths were read in water under a microscope with reflected light. The sex proportion was determined based on the fish collected for length measurements, while gonads maturity was based on the examination of 468 specimens (additional sample was taken). The gonad maturity stage was determined according to a 6- grade scale: immature (I), early maturing-A (II), maturing-B (III), late maturing-C (IV), spawning (V) and resting (VI). (Ridget, F., J. Boje. 1989, Fishery and some biological aspects of Greenland halibut (Reinhardtius hippoglossoides) in West Greenland waters. NAFO Sci. Coun. Studies 13: 41-52.).
The relationship between body length and weight was calculated using the formula W = k * Ln
where:
W – weight of fish (g);
L – length of fish (cm);
k and n – constant coefficients.
Tagged Greenland halibut and the incidental mortality of birds and mammals were also recorded.
The CPUE was calculated for each square to determine the distribution of Greenland halibut in the survey area. Catches from each haul were standardized to one hour of trawling and to one square kilometer of trawling surface according to the following formulae:
1. t
CPUE=W
2. D p
CPUE W
= × where:
CPUE – catch per unit effort (1- kg/h and 2 - kg/km2);
W – weight of catch (kg);
t – duration of trawl (hours);
D – towing distance (km);
p – horizontal opening of the net (km).
The area swept by the trawl was defined as the distance between the wings multiplied by the towed distance. It was assumed that the catchability coefficient for Greenland halibut was 1; therefore, the total effect of escapement of fish was equal to 0. The mean catch rates (t/hr) and density (t/km2) were calculated for each square.
The “swept area” method was also used to determine the biomass of Greenland halibut at depth strata and in the total survey area according to the formula:
q A B CPUE×
= where:
B - biomass (tons);
CPUE - catch per unit effort (t/km2);
A – area of survey (km2);
q – catchability coefficient.
3. Vessel and gear specifications 3. 1. Characteristics of the vessel Name: POLONUS GDY-36 Nationality: POLISH
Registration port and number: GDYNIA, GDY-36
Overall length: (in meters) 60.33 Maximum draught: (in meters) 7.00 GRT: 1805
Net tonnage: 563
Propulsion e.g. diesel/steam: DIESEL Call sign: SNHE
3. 2. Description of gear
Bottom trawl type – BACALO 630 Float rope: 70.2 m
Ground rope: 39.8 m
Vertical opening of trawl: 5 m
Average net opening between wings: 14.0 m NET
Bag of coral 30 m with 140 mm mesh size Codend of nylon with 40 mm mesh size GROUND GEAR:
Central section 39.8 m with 21” rubber discs DOORS:
Type of doors - INJECTOR 9.5 m² Weight of doors - 4000 kg
FLOATS :
Number of floats - 210 Float diameter - 250 mm LEGS - 60/75 m
BRIDLES – 140 m
The diagram of the net used in the fishing survey is presented in Figure 4 4. Results
4. 1. Species composition of catches
A total 203.4 tons of fish were caught during the fishing survey. Greenland halibut dominated the catches by weight and contributed nearly 98.3% of the total catch (Table 1). Bycatch was only 3467 kg and consisted of 16 fish species. The most abundant species were redfish (Sebastes mentella) – 1760 kg and cod (Gadus morhua) – 1302 kg. All 16 bycatch species with a weight of 2815 kg were noted in the shallower strata (500-699m), 13 species with a weight of 585 kg were noted in
in the deepest strata (1000-1200m). The species composition of catches by depth strata in numbers and weights of specimens is presented in Table 2.
The S. mentella, which was most numerous bycatch species, consisted of fish measuring from 30 to 44cm in length, while more than 80% of these fish were between 33 to 37cm.
Neither sea birds nor mammals were noted in the net during the cruise.
4. 2. Catch rates
A total of 54 squares were designated in the trawl survey area at the three depth strata between the latitudes of 73o 30’N and 76o 30’N. The total surface of the survey area was calculated at 7844 km2 of which 2078 km2 was at the shallower depth strata, 3346 km2 at the deeper strata, and 2420 km2 at the deepest strata. The average catch rate of Greenland halibut throughout the survey area was 1.34 t/hr. In the shallower and deeper strata the catch rates were nearly similar (1.50 and 1.63 t/hr, respectively), but in the deepest strata the catch rate was very low at just 0.09 t/h. There were also significant differences in catch rates among the squares. Higher catch rates were observed in the vicinity of Bear Island in the shallower and deeper strata. The lowest CPUE was observed in the northern part of the survey area. Table 3 presents the catch of Greenland halibut and catch rates in kg per hour of trawling calculated for each square.
4. 3. Biological characteristics of Greenland halibut
Length measurements of fish, segregated by sex, were collected from 6085 halibut specimens. The length of the halibut ranged from 28 to 98cm TL at a mean length of 50.2 cm. The length compositions at the three depth strata are presented in Figure 5 and the length distribution of fish (males and females) in each sampled haul is presented in Annex 1 (available only in the Report sent to the Institute of Marine Research, Bergen, Norway). The length distribution differed among the depths and fish length decreased with depth. In the shallower waters to 700m the mean length was 51.7cm, in the deeper waters it was 48.6cm, while in the deepest strata the mean length of halibut was the smallest at 46.9cm. Mean lengths of Greenland halibut sampled in April 2007 by depth strata and sex are presented in Table 4.
It was also noted that the halibut length distribution depended on water temperature at towing depth. This was indicated by the share of larger fishes (older) increasing in catches performed where water temperature was higher (Fig. 6).
Otoliths collected during biological analysis from 262 Greenland halibut specimens were used for age determinations. The age composition of catches was calculated from an age-length key and is presented in Figure 7. Males dominated the younger age groups but Greenland halibut from 10 years old were mostly females and the fish after 13 years old were all females (Fig. 7a). Three generation 1999, 2000 and 2001 dominated during the survey (Fig. 7b). The determinate age of Greenland halibut collected during the survey is included in Annex 2 (available only in the Report sent to the Institute of Marine Research, Bergen, Norway).
The sex ratio was calculated from 6085 specimens during length measurements. Males dominated in the catches and comprised nearly 58% of the sampled fish. The share of males in the stock was much higher in the shallower and deeper strata (65.3 and 63.4%, respectively) than in the deepest strata where males comprised 51.3% (Fig. 5).
Maturity stage data were collected for 468 halibut specimens. Observations of gonad maturity indicated that most males (nearly 55%) had gonads in the maturing stage while a decided part of fish was spawning (nearly 27%). Most of the females were in pre-spawning stages and their gonads were in maturing and late maturing stages (23 and 33%, respectively). Only 8% of females were actively spawning (Table 5).
Weight was recorded for 262 halibut specimens. Greenland halibut attained weights ranging from 160g to 9200g. The mean weight of the sampled males was 937g while that of females was 2374g. The weight of fish at length classes is presented in Table 6. The relationship between body length and weight for the sexes combined was calculated as W(g) = 0.0039 * TL (cm)3.2031. The length-weight relationship for males and females are presented in Figure 8.
The examination of halibut stomachs indicated that feeding was very weak.
About 80% of the fish had empty stomachs (Table 7). While no detailed examinations of food composition were conducted, undigested fish, squids, and shrimps dominated in the stomachs.
All biological data, including age of Greenland halibut collected during the cruise are presented in Annex 2 (available only in the Report sent to the Institute of Marine Research, Bergen, Norway).
4. 4. Density, abundance, and biomass of Greenland halibut in the survey area The density of Greenland halibut in kg/km2 for each square and depth strata was estimated with the swept area method. The results presented in Table 8 show the density of Greenland halibut calculated for each square in the depth strata. Results indicated that density was very low in the deepest strata (1.1 t/km2) while in the deeper strata it was 20.4 t/km2 and a little less in shallower strata (18.6 t/km2).
Relative and stable high density of fish was observed mainly between the latitudes 74o00’ and 75o50’N in the deeper and shallower strata. The highest value of
Greenland halibut density was calculated for the squares in the vicinity of Bear Island. Density is presented graphically in Figure 9.
The analysis of the distribution of the bottom water temperature in the survey area indicates that Greenland halibut prefer a water temperature of about 2oC where the density of walleye pollock stock was higher (Fig. 10). The lower density in the southern part of survey area despite higher water temperature is probably caused by very weak migration of Greenland halibut farther to the south.
The total standing biomass of Greenland halibut in the survey area calculated as the sum of biomass in each square was estimated to be 99.0 thousand tons, of this 61.6% of the fish inhabited the deeper depth strata (700-1000m) during the time of the survey (Table 8).
4. 5. Other information
Five tagged specimens of Greenland halibut were caught during the survey.
Unfortunately, four of them had been headed before the tags were noted, so it was difficult to obtain a full biological description of these fishes. A protocol was prepared for each of the tagged fish, and all the available fishery and biological data were included. Five tags of the fish with protocols were sent to the Institute of Marine Research in Bergen, Norway on June 21, 2007. The protocols are also included in Annex 3. The both otoliths of the Greenland halibut TAG: NO. 20684; 5817 BERGEN are attached to protocol 1. The age of the fish was determinate as 7 years.
TABLES
Table 1. Catch by species in Polish fishing survey in ICES IIb Area in April 2007
Common name Scientific name Total catch Promille by catch Greenland halibut Reinhardtius hippoglossoides 199 975,05 982.960
Redfish Sebastes mentella 1 760,83 8.655
Cod Gadus morhua 1 302,00 6.400
Spinetail ray Bathraja spinacauda 180,22 0.886
Esmarks eelpout Lycodes esmarki 67,72 0.333
Roughhead granadier Macrourus berglax 50,84 0.250
Spotted wolffish Anarhichas minor 47,59 0.234
Round ray Raja fyllae 15,10 0.074
Blue whiting Micromesistius potassou 10,80 0.053
Haddock Melanogrammus aeglefinus 9,74 0.048
Wolf-fish Anarhichas lupus 9,40 0.046
Lumpsucker Cyclopterus lumpus 5,67 0.028
Saithe Pollachius virens 2,19 0.011
Argentina Argentina silus 2,15 0.011
Dab Limanda limanda 1,58 0.008
Arctic rockling Onagadus sp. 0,51 0.003
Arctic sculpin Cottunculus microps 0,22 0.001
Total 203 441.61
Table 2 . Species composition of catches by depth strata, number and weight of specimens in April 2007
Subarea S (500-699m) Subarea D (700-999m) Subarea DD (1000-1200m) Research area
Common name Scientific name
No of
caught Weight of fish (kg)
Mean weight of fish (kg)
No of
caught Weight of fish (kg)
Mean weight
of fish (kg)
No of
caught Weight of fish (kg)
Mean weight
of fish (kg)
No of caught
Range of length
(cm)
Weight of fish (kg)
Mean weight
of fish (kg) Greenland halibut Reinhardtius
hippoglossoides 91 297 124 735.95 1.37 65 792 73 211.10 1.11 1 987 2 028.00 1.02 159 076 28 - 98 199 975.05 1.26
Redfish Sebastes mentella 2 805 1 515.13 0.54 455 245.70 0.54 3 260 30 - 44 1 760.83 0.54
Cod Gadus morhua 346 1 009.05 2.92 89 260.40 2.93 11 32.55 2.96 446 41 - 108 1 302.00 2.92
Spinetail ray Bathraja spinacauda 50 128.96 2.58 10 23.20 2.32 15 28.06 1.87 75 25 - 75 180.22 2.40
Esmarks eelpout Lycodes esmarki 109 61.83 0.57 10 5.33 0.53 1 0.57 0.57 120 28 - 65 67.72 0.56
Roughhead granadier Macrourus berglax 8 43.97 5.50 4 4.55 1.14 3 2.32 0.77 15 40 - 82 50.84 3.39
Spotted wolffish Anarhichas minor 7 10.58 1.51 2 37.01 18.51 9 59 - 73 47.59 5.29
Round ray Raja fyllae 16 13.41 0.84 2 1.70 0.85 18 30 - 55 15.10 0.84
Blue whiting Micromesistius
potassou 58 7.93 0.14 21 2.87 0.14 79 24 - 34 10.80 0.14
Haddock Melanogrammus
aeglefinus 4 6.55 1.64 2 3.19 1.60 6 48 - 63 9.74 1.62
Wolf-fish Anarhichas lupus 4 9.40 2.35 4 60 - 120 9.40 2.35
Lumpsucker Cyclopterus lumpus 2 2.30 1.15 1 3.37 3.37 3 30 - 41 5.67 1.89
Saithe Pollachius virens 2 2.19 1.10 2 51 - 52 2.19 1.10
Argentina Argentina silus 5 1.90 0.38 1 0.25 0.25 6 36 - 38 2.15 0.36
Dab Limanda limanda 8 1.42 0.18 1 0.16 0.16 9 23 - 32 1.58 0.18
Arctic rockling Onagadus sp. 1 0.21 0.21 1 0.30 0.30 2 26 - 33 0.51 0.25
Arctic sculpin Cottunculus microps 2 0.10 0.05 1 0.12 0.12 3 13 - 17 0.22 0.07
Total 94 724 127 550.85 66 391 73 795.87 2 018 2 094.87 163 133 203 441.60
Table 3 . Catch and CPUE of Greenland halibut by depth strata and squares in April 2007
S Square No
of hauls
Catch (kg) CPUE
(kg/h) D Square No of hauls
Catch
(kg) CPUE
(kg/h) DD Square No of hauls
Catch
(kg) CPUE (kg/h) s-01 2 3 313.0 0.925 d-01 1 2 272,4 1.136 dd-01 0.131 s-02 1 6 179.1 1.399 d-02 1 4 836,0 1.707 dd-02 1 273,0 0.131 s-03 1 4 407.0 1.322 d-03 1 4 502,0 1.125
s-04 1 2 925.0 1.064 d-04 1 5 070,0 1.844 dd-03 & dd-04 1 273,0 0.131 s-05 1 4 364.1 2.182 d-05 1 8 970,0 2.990
s-06 2 10 007.1 1.430 d-06 1 3 861,0 1.782 dd-05 & dd-06 1 780,0 0.425 s-07 2 20 724.0 2.391 d-07 1 5 224,4 1.741
s-08 2 10 842.0 1.859 d-08 1 8 619,0 2.298 dd-07 & dd-08 1 78,0 0.028 s-09 1 8 853.0 1.660 d-09 1 6 880,2 2.231
s-10 3 15 039.1 1.111 d-10 1 1 599,0 0.872 dd-09 & dd-10 1 39,0 0.015 s-11 2 14 513.1 1.371 d-11 1 7 249,7 1.706
s-12 2 11 284.5 2.006 d-12 1 4 420,7 1.263 dd-11 & dd-12 1 273,0 0.113 s-13 1 3 900.0 1.337 d-13 1 2 808,0 2.407
s-14 1 4 134.0 1.711 d-14 1 2 271,0 1.817 dd-13 & dd-14 1 39,0 0.014 s-15 1 1 287.0 0.908 d-15 1 1 911,0 0.740
s-16 1 1 404.0 1.203 d-16 1 572,0 0.458 dd-15 & dd-16 1 156,0 0.069 s-17 1 1 326.0 1.061 d-17 1 858,0 0.735
Shallower depth strata (500-699m)
s-18 1 234.0 0.187
Deeper depth strata (700-999m)
d-18 1 1 287,0 1.030
Deepest depth strata (1000-1200m)
dd-17 & dd-18 1 117,0 0.044 Total 26 124 736.0 1.501 Total 18 73 211.1 1.633 Total 9 2 028,0 0.094
Table 4. Mean length of Greenland halibut sampled in April 2007 by depth strata
Sex (500-699m) Subarea S
Subarea D (700-999m)
Subarea DD
(1000-1200m) Research area
Males 48,0 46,6 44,6 47,2
Females 55,6 52,6 51,0 54,4
Males and females 51,7 48,6 46,9 50,2
Table 5. Maturity stages of Greenland halibut sampled in April 2007
Maturity stages Sex
I II III IV V VI Total
N 1 26 125 15 61 228 Males
% 0,4 11,4 54,8 6,6 26,8 0,0
N 85 56 79 19 1 240 Females
% 0,0 35,4 23,3 32,9 7,9 0,4
N 1 111 181 94 80 1 468 Total
% 0,2 23,7 38,7 20,1 17,1 0,2
Table 6. Mean weight of Greenland halibut in length classes in April 2007
Males Females Males and Females
Length
classes (cm) n Mean weight
( g ) n Mean weight
( g ) n Mean weight ( g )
28 1 160,0 1 160,0 30 1 205,0 1 205,0 32 1 255,0 1 255,0 33 2 267,5 1 250,0 3 261,7 34 4 325,0 2 277,5 6 309,2 35 3 345,0 4 327,5 7 335,0 36 3 395,0 1 400,0 4 396,3 37 4 402,5 3 398,3 7 400,7 38 2 412,5 2 487,5 4 450,0 39 5 524,0 2 472,5 7 509,3 40 3 508,3 2 567,5 5 532,0 41 5 577,0 3 588,3 8 581,3 42 4 598,8 3 625,0 7 610,0 43 4 672,5 2 655,0 6 666,7 44 4 655,0 3 695,0 7 672,1 45 7 767,1 3 875,0 10 799,5 46 5 868,0 3 863,3 8 866,3 47 3 866,7 3 996,7 6 931,7 48 4 925,0 3 983,3 7 950,0 49 3 968,3 3 1063,3 6 1015,8 50 11 1100,0 3 1096,7 14 1099,3 51 4 1172,5 4 1261,3 8 1216,9 52 5 1137,0 4 1286,3 9 1203,3 53 2 1220,0 3 1388,3 5 1321,0 54 5 1345,0 4 1465,0 9 1398,3 55 6 1355,8 2 1475,0 8 1385,6 56 4 1541,3 3 1555,0 7 1547,1 57 1 1850,0 6 1783,3 7 1792,9 58 4 1597,5 3 1893,3 7 1724,3 59 2 1762,5 3 1840,0 5 1809,0 60 2 1915,0 2 2005,0 4 1960,0 61 2 1980,0 3 2023,3 5 2006,0 62 1 2090,0 4 2225,0 5 2198,0 63 1 2200,0 5 2225,0 6 2220,8 64 2 2265,0 2 2265,0 65 4 2265,0 4 2265,0 66 4 2643,8 4 2643,8 67 1 2505,0 1 2505,0 68 2 2605,0 2 2605,0 69 1 2880,0 1 2880,0 70 2 3442,5 2 3442,5 71 3 3333,3 3 3333,3 72 2 3330,0 2 3330,0 73 2 3742,5 2 3742,5 74 2 3215,0 2 3215,0 75 2 4035,0 2 4035,0 77 3 3763,3 3 3763,3 78 1 4470,0 1 4470,0 79 1 4660,0 1 4660,0 80 2 4765,0 2 4765,0 82 1 5230,0 1 5230,0 83 2 5830,0 2 5830,0 84 2 5650,0 2 5650,0 86 1 6090,0 1 6090,0 87 1 6320,0 1 6320,0 88 1 6550,0 1 6550,0 89 3 6910,0 3 6910,0 90 4 6971,3 4 6971,3 92 1 7520,0 1 7520,0 93 1 7800,0 1 7800,0 98 1 9200,0 1 9200,0 Mean weight
(g) 118 936.8 144 2373.5 262 1726.5
Table 7. Fullness of Greenland halibut stomachs in April 2007
Fullness of halibut stomachs
Sex 0 1 2 3 4 Total
N 92 8 6 6 6 118 Males
% 78,0 6,8 5,1 5,1 5,1
N 115 7 9 6 7 144 Females
% 79,9 4,9 6,3 4,2 4,9
N 207 15 15 12 13 262 Total
% 79,0 5,7 5,7 4,6 5,0
Table 8. Biomass of Greenland halibut in research area by depth strata and squares in April 2007.
Subarea Density
(t/km2) Biomass (t) Subarea Density
(t/km2) Biomass (t) Subarea Density
(t/km2) Biomass (t)
S-01 10.5 1 754 D-01 12.9 4 594 DD-01 1.3 235
S-02 16.6 2 252 D-02 18.8 5 109 DD-02 1.3 231
S-03 18.2 2 060 D-03 17.4 2 340 DD-03 1.5 164
S-04 12.4 1 280 D-04 20.9 3 308 DD-04 1.5 126
S-05 25.5 1 569 D-05 34.9 4 026 DD-05 5.0 418
S-06 18.1 964 D-06 20.8 1 719 DD-06 5.0 354
S-07 32.7 2 803 D-07 20.4 2 434 DD-07 0.3 38
S-08 26.1 3 256 D-08 34.1 4 912 DD-08 0.3 26
S-09 21.6 2 400 D-09 28.7 4 810 DD-09 0.2 19
S-10 15.8 2 067 D-10 10.2 1 940 DD-10 0.2 28
S-11 18.1 2 396 D-11 28.6 5 356 DD-11 1.3 210
S-12 26.9 3 887 D-12 17.4 3 353 DD-12 1.3 212
S-13 15.6 2 786 D-13 27.3 6 464 DD-13 0.2 27
S-14 19.4 1 864 D-14 20.6 3 823 DD-14 0.2 22
S-15 10.3 933 D-15 8.4 1 513 DD-15 0.8 111
S-16 13.7 1 397 D-16 5.2 973 DD-16 0.8 128
S-17 12.0 1 520 D-17 8.3 1 854 DD-17 0.5 72
S-18 2.1 259 D-18 11.7 2 492 DD-18 0.5 93
Total S 18.5 35 447 Total D 20.4 61 019 Total DD 1.1 2 514
FIGURES
Figure 1. Polish fishing vessel “Polonus”
Figure 2. The depth strata and squares in Polish fishing survey area in April 2007
Figure 3. Geographical positions of control hauls and direction of trawling during Polish trawl
Figure 4. Schema of the net Bacalao 630
0 1 2 3 4 5 6 7
25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Length (cm)
Frequency (%)
Total
Males (n=1672; 51,3%) Females (n=1587; 48,7%)
500 - 699m
0 1 2 3 4 5 6 7
25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Length (cm)
Frequency (%)
Total
Males (n=1674; 65,3%) Females (n=890; 34,7%)
700 - 999m
0 1 2 3 4 5 6 7
25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Length (cm)
Frequency (%)
Total
Males (n=166; 63,4%) Females (n=96; 36,6%)
1000 - 1200m
Figure 5. Length compositions of Greenland halibut (by depth strata) in Polish trawl survey in April 2007
0 5 10 15 20 25 30
< 30 31-35 36-40 41-45 46-50 51-55 56-60 61-65 66-70 71-75 76-80 81-85 86-90 > 90 Length classes (cm)
Frequency (%) -1.0° ÷ 1.0°C
1.0° ÷ 2.5°C Water temperature on the depth of trawl
Figure 6. The frequency of the halibut length classes depending on the bottom water temperature in April 2007
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Age groups
Frequency (%)
Males (n = 118) Females (n = 144) a)
0.0 5.0 10.0 15.0 20.0 25.0
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Age groups
Frequency (%)
Males and Females b)
Fig. 7. Age composition of Greenland halibut (from age-length key) in Polish trawl survey in April 2007
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
28 36 41 46 51 56 36 41 46 51 56 62 67 72 77 82 87 92 97
Length classes (cm)
Weight (g)
Males
n = 118
W(g) = 0,0061×TL(cm)3,0825
R2 = 0,954
Females
n = 144
W(g) = 0,0044×TL(cm)3,177 R2 = 0,970
Figure 8. Length-weight relationship for Greenland halibut (males and females) in April 2007
Figure 9. Density of Greenland halibut (tons/km2)in the Polish trawl survey in April 2007
ANNEX 3.
Protocol no 1
Number of TAG: NO. 20684; 5817 BERGEN
Species: Greenland halibut (Reinhardtius hippoglossoides) Date of catch: 6 April 2007
Position of catch: LAT: 74°51'2 N LON: 015°30'3 E Time: 07.00 LT
Vessel: f/v Polonus
Type of cruise: fishing survey Depth: 700-745 m
Temperature at the bottom: - 0.3 – 0.7°C Length: 44 cm
Weight: 615 g Age: 7 years Sex: Male
Gonad’s maturity: 3 Stomach fullness: 0 Remarks: photo
Protocol no 2
Number of TAG: nr 193754 N
Species: Greenland halibut (Reinhardtius hippoglossoides) Date of catch: 7 April 2007
Position of catch: LAT: 75°20'0 N LON: 014°20'7 E Time: 08.15 LT
Vessel: f/v Polonus
Type of cruise: fishing survey Depth: 704-712 m
Temperature at the bottom: -0.1 - 0.2°C
Remarks: the mark was found on the fish without head and tail (dressed)
Protocol no 3
Number of TAG: No. GH03327
Species: Greenland halibut (Reinhardtius hippoglossoides) Date of catch: 8 April 2007
Position of catch: LAT: 75°30,0 N LON: 014°14'9 E Time: 05.25 LT
Ship: f/v Polonus
Type of cruise: fishing survey Depth: 510-678 m
Temperature at the bottom: 1.5-1.6°C
Remarks: the mark was found on the fish without head and tail (dressed)
Protocol no 4
Number of TAG: NO. 14791
Species: Greenland halibut (Reinhardtius hippoglossoides) Date of catch: 10 April 2007
Position of catch: LAT: 75°10'6 N LON: 015°06'5 E Time: 23.40 LT
Ship: f/v Polonus
Type of cruise: fishing survey Depth: 541-611 m
Temperature at the bottom: 0.7 - 2.2°C
Remarks: the mark was found on the fish without head and tail (dressed)
Protocol no 5
Number of TAG: No. GH033848
Species: Greenland halibut (Reinhardtius hippoglossoides) Date of catch: 11 April 2007
Position of catch: LAT: 74°57'9 N LON: 015°37'6 E Time: 04.50 LT
Vessel: f/v Polonus
Type of cruise: fishing survey Depth: 622-653 m
Temperature at the bottom: 0.1 - 1.4°C
Remarks: the mark was found on the fish without head and tail (dressed)
